JP4992535B2 - Rolling bearing - Google Patents

Description

  The present invention relates to a rolling bearing.

Ball screws used in electric injection molding machines, press machines, etc. are relatively large and are loaded with high loads. They are used with short strokes where high loads act instantaneously, and the maximum load is applied. It is used under severe conditions such as once rotating in a state and then reversely rotating (reciprocating).
Since the ball screw for this application requires high speed control and improved positioning accuracy, the rolling bearing that supports this ball screw may not have a low torque or a sudden torque fluctuation such as a torque spike. It has been demanded. In addition, the rolling bearings for this application are susceptible to vibrations due to the operation of the equipment, and because the lubrication conditions are severe in order to suppress the evaporation and scattering of the lubricating oil, it is in an environment where fretting and seizure are likely to occur on the raceway surface. .

On the other hand, FIG. 3 schematically shows a belt type continuously variable transmission of a vehicle, and the rotation shafts of the primary pulley 7 and the secondary pulley 8 are respectively a pair of rolling bearings 11a, 11b, 12a, 12b. It is supported. Reference numeral 9 denotes a belt.
Rolling bearings used in vehicle belt type continuously variable transmissions are required to improve power transmission efficiency by belts, to suppress belt drive noise, and to suppress wear of pulleys and belts. From these points, it is desirable to use a lubricating oil having high fluidity (low viscosity).

  However, the use of highly fluid lubricating oil is not preferable in terms of the lubricating performance of the rolling bearing that supports the rotating shaft of the pulley. That is, since the rolling bearing that supports the rotating shaft of the pulley is located on the side surface of the pulley, it is difficult to supply lubricating oil to the rolling bearing, and the lubrication between the race and the rolling element is caused by the vibration described above. The state of the film is likely to deteriorate, and the lubricating film is likely to be destroyed due to the influence of slippage. Therefore, the rolling bearing used in the belt type continuously variable transmission is in an environment where fretting and seizure are likely to occur on the raceway surface.

  As a conventional method for improving the fretting resistance and seizure resistance of a rolling bearing, the constituent members (the race ring and the rolling element) of the rolling bearing are made of SUJ2 steel, and at least one of them is subjected to quenching and tempering after nitriding treatment. There are a method and a method of making the rolling elements made of ceramics. However, in the case of a rolling bearing that supports a ball screw used in an electric injection molding machine or a press machine, or a rolling bearing that is used in a belt type continuously variable transmission, sufficient effects can be obtained by these methods. I can't.

In contrast to these prior arts, for example, in Patent Document 1 below, a turbocharger, a machine tool, or the like is used in a high-speed rotation environment in which the dm · n value is 1.0 × 10 ⁶ or more. However, a technique for preventing the rolling bearing from being worn or seized is described. This technology improves the wear resistance and seizure resistance by specifying the steel to be used and allowing carbon and nitrogen to exist in the surface layer at a predetermined content or by depositing TiC of 0.1 μm or less on the surface. I am letting.
JP 2000-45049 A

Even in the technique described in Patent Document 1, in the case of a rolling bearing that supports a ball screw used in an electric injection molding machine or a press machine, or a rolling bearing used in a belt type continuously variable transmission, the rolling bearing is used. There is room for further improvement in terms of improving the fretting resistance and seizure resistance.
An object of the present invention is excellent in fretting resistance and seizure resistance, suitable as a rolling bearing for supporting a ball screw used in an electric injection molding machine, a press machine, etc., or a rolling bearing for a belt type continuously variable transmission. It is to provide a rolling bearing.

  In order to solve the above-described problems, the present invention provides a rolling element having a carbon (C) content of 0.3 mass% to 1.2 mass% and a chromium (Cr) content of 0.5 mass%. 2.0 mass% or less, silicon (Si) content of 0.4 mass% or more and 1.2 mass% or less, manganese (Mn) content of 0.4 mass% or more and 1.2 mass% or less, After the total content of silicon (Si) and manganese (Mn) is 1.0% by mass or more and 2.0% by mass or less, the remaining iron and the steel material which is an unavoidable impurity are processed into a predetermined shape, and then subjected to nitriding treatment Alternatively, it is obtained by performing heat treatment comprising carbonitriding and quenching and tempering, and the rolling surface is made of silicon (Si) nitride and manganese (Mn) nitride, and Si · Mn having a particle size of 1 μm or less. System nitride exists in an area ratio of 1% or more and 10% or less. Austenite provides a rolling bearing, characterized in that it is 10% by volume or less.

  In the rolling bearing of the present invention, the bearing ring has a carbon (C) content of 0.2 mass% to 1.2 mass% and a chromium (Cr) content of 0.5 mass% to 2.0 mass%. % Or less, silicon (Si) content of 0.1% by mass or more and 0.5% by mass or less, manganese (Mn) content of 0.1% by mass or more and 0.5% by mass or less, balance iron and inevitable It is preferable that the steel material, which is an impurity, is processed into a predetermined shape and then heat-treated.

According to the rolling bearing of the present invention, a high hardness Si / Mn nitride having a particle diameter of 1 μm or less is present on the rolling surface of the rolling element in an area ratio of 1% or more, and the surface layer portion of the rolling surface is When the retained austenite is 10% by volume or less (0% by volume or more, preferably 3% by volume or more), the wear resistance and seizure resistance when used at high speed and high temperature are increased.
If the abundance of Si · Mn nitride having a particle size of 1 μm or less on the rolling surface exceeds 10% in terms of area ratio, the grindability may deteriorate or the toughness may decrease and cracks may occur. Moreover, when the retained austenite of the surface layer part of a rolling surface exceeds 10 volume%, surface hardness will fall and fretting resistance will become inadequate.

  This rolling element has a carbon (C) content of 0.3 mass% to 1.2 mass%, a chromium (Cr) content of 0.5 mass% to 2.0 mass%, silicon (Si ) Content of 0.4 mass% or more and 1.2 mass% or less, manganese (Mn) content of 0.4 mass% or more and 1.2 mass% or less, the sum of silicon (Si) and manganese (Mn) It was obtained by processing a steel material having a content ratio of 1.0% by mass or more and 2.0% by mass or less into a predetermined shape, and then performing a heat treatment including nitriding or carbonitriding, quenching and tempering. Is.

The content rate of the alloy component of the steel constituting the material to be used was set to the above range for the following reason.
When the carbon (C) content is less than 0.3% by mass, it takes time to allow a sufficient amount of carbon to be present in the surface layer portion by carbonitriding. Therefore, the carbon (C) content is set to 0.3% by mass or more, preferably 0.5% by mass or more, and more preferably 0.7% by mass or more.
On the other hand, if the carbon (C) content exceeds 1.2 mass%, giant carbides are formed during steelmaking, which may adversely affect the quenching characteristics and rolling fatigue life. In addition, cold workability may be reduced, leading to an increase in manufacturing cost.

When the content of chromium (Cr) is less than 0.5% by mass, the effect of increasing hardenability and temper softening resistance and the effect of forming high-hardness fine carbides or carbonitrides are substantially obtained. I can't get it. In order to obtain these effects sufficiently, the chromium (Cr) content is preferably 1.3% by mass or more.
On the other hand, if the chromium (Cr) content exceeds 2.0 mass%, giant carbides are formed during steelmaking, which may adversely affect the quenching characteristics and rolling fatigue life. In addition, cold workability and machinability may decrease, leading to an increase in manufacturing cost. Therefore, the content of chromium (Cr) is preferably 1.6% by mass or less.

When the content of silicon (Si) and manganese (Mn) is less than 0.4% by mass, and the total content of silicon (Si) and manganese (Mn) is less than 1.0% by mass, the particle size is 1 μm. The following Si · Mn nitrides cannot be present on the rolling surface in an area ratio of 1% or more and 10% or less.
If the content of silicon (Si) exceeds 1.2% by mass, the toughness of steel becomes insufficient. If the content of manganese (Mn) exceeds 1.2% by mass, the forgeability and machinability are lowered, and it tends to exist as inclusions together with sulfur (S) phosphorus (P) which is an impurity in steel. When the total content of silicon (Si) and manganese (Mn) exceeds 2.0 mass%, a large amount of Si · Mn nitride is precipitated, and machinability and toughness are deteriorated.

In addition, the steel which makes the raw material used by this invention may contain carbide | carbonized_material formation promotion elements, such as molybdenum (Mo) and vanadium (V) other than the above-mentioned alloy component. In that case, it is made to contain in the ratio of 2 mass% or less in the range which does not raise the cost by material cost or workability fall, respectively. And the steel which makes the raw material used by this invention is the remainder except iron (Fe) and an unavoidable impurity (S, P, Al, Ti, O, etc.) except the component to contain selectively and the above-mentioned alloy component. Composed.
In the rolling bearing according to the present invention, the Si / Mn nitride having a particle size of 1 μm or less is present on the rolling surface of the rolling element in an area ratio of 1% or more and 10% or less. The number of Si · Mn nitrides having an area of 375 μm ² that is 0.05 μm or more and 1 μm or less is preferably 100 or more.

  When the area ratio of the nitride is the same, the smaller the particle size, the greater the number of particles present, and the shorter the interparticle distance, so that the precipitation strengthening ability increases. Therefore, the number of fine nitrides having an average particle size of 0.05 μm or more and 1 μm or less is increased within a range of 1 to 10% of the area ratio of Si / Mn nitride using steel with a large content of Si and Mn. This leads to further strengthening of the rolling surface. Furthermore, the rolling surface is further strengthened by setting the ratio of the Si · Mn nitride of 0.05 to 0.50 μm in the Si · Mn nitride of 0.05 μm to 1 μm to 20% or more. Is possible.

  According to the present invention, it is excellent in fretting resistance and seizure resistance, which is suitable as a rolling bearing for supporting a ball screw used in an electric injection molding machine or a press machine, or a rolling bearing for a belt type continuously variable transmission. A rolling bearing is obtained.

Hereinafter, embodiments of the present invention will be described.
FIG. 1 is a cross-sectional view showing a deep groove ball bearing corresponding to an embodiment of the present invention.
This bearing includes an inner ring 1, an outer ring 2, balls (rolling elements) 3, and a cage 4.
As the deep groove ball bearing shown in FIG. 1, one corresponding to the reference number 6206 was produced as follows.
The ball 3 was obtained by processing a material made of various steels shown in Table 1 below into a predetermined shape by cold forming, then heat-treating under the following conditions, and then grinding. In Table 1, numerical values that deviate from the configuration of the present invention are underlined.

  The abundance of Si · Mn nitride having a particle size of 1 μm or less on the surface (rolling surface) of each ball 3 was measured by the following method. Moreover, about the surface (rolling surface) of each obtained ball 3, the retained austenite of the surface layer part was measured by the X-ray diffraction method. These results are shown in Table 2 below.

[Heat treatment conditions]
Submerged quenching: Oil cooling after holding at 820-870 ° C. for 0.5-1.0 hours in R _X gas atmosphere.
Quenching the carburized: Enrich 1.0 to 5.0 hours after held at from 820 to 880 ° C. in a gas atmosphere, allowed to cool, then, 0.5 to 1.0 hours 820 to 870 ° C. in R _X gas atmosphere After holding, oil cooling.

Quenching after nitriding: holding at 820 to 920 ° C. in an atmosphere of R _X gas + ammonia gas for 1.0 to 5.0 hours, allowing to cool, and then 0.5 to 820 to 870 ° C. in an atmosphere of R _X gas Oil cooling after holding for 1.0 hour.
Quenching after carbonitriding: Holding at 820 to 920 ° C. in an atmosphere of R _X gas + enriched gas + ammonia gas for 1.0 to 5.0 hours, allowing to cool, and then to 820 to 870 ° C. in an R _X gas atmosphere Oil holding after holding for 0.5-1.0 hours.
After any of the above treatments is performed for each sample, tempering is performed for all samples by holding at 150 to 300 ° C. for 3 hours.

[Method of measuring the abundance of Si / Mn nitride]
A plate-shaped test piece is produced in the same process as each ball 3 with the same machining allowance, and the surface is accelerating voltage 10 kV, magnification 5000 using a field emission scanning electron microscope (FE-SEM). The ratio of the total area of Si nitride and Mn nitride having a particle size of 1 μm or less in the observed image was measured by an image analyzer. Observation was performed in three or more fields of view, and the average value of all fields of view was calculated as the abundance ratio of Si / Mn nitride.
Further, as the inner ring 1 and the outer ring 2, those made of SUJ2 and subjected to normal heat treatment including soaking were used, and the cage 4 was made of steel.

〔An endurance test〕
The deep groove ball bearing of FIG. 1 was assembled using each of the balls 3 thus obtained, the inner ring 1, the outer ring 2, and the cage 4, and subjected to a rotation tester. And traction oil "VG68" is used as the lubricating oil, and foreign matter is mixed (iron powder with Hv800, particle size of 100 μm or less is 50%, 100-200 μm is 50%, 0.15 g / L) Under lubrication, the inner ring was rotated under the conditions of an axial load: 6370 N (650 kgf) and a rotational speed: 3500 min ⁻¹ . The time until the torque became three times the initial value was measured as “endurance life”. In addition, 10 bearings were assembled and tested for each sample, and the L10 life was calculated.
Then, by dividing the L10 life of each sample by the L10 life of sample No. 9, a “durable life ratio” was obtained in which the seizure life of sample No. 9 was “1”. The results are also shown in Table 2 below.

[Abrasion test]
In addition, two cylindrical test bodies for “two-cylinder wear test” were prepared in the same manner as the balls 3 of sample Nos. 1 to 16, and the wear test was performed as follows under the following conditions.
First, a pair of cylindrical specimens are mounted on a pair of rotating shafts opposed in the vertical direction. Next, a load is applied to the upper specimen, both specimens are brought into contact, and one specimen is driven to rotate while spraying lubricating oil from the nozzle at the contact position, thereby sliding both specimens in opposite directions. Rotate. Then, after rotating by a predetermined distance, the amount of wear is measured, and the amount of wear per unit slip distance (1 m) (total weight reduction amount of both specimens) is calculated. The calculated values are also shown in Table 2 below.

<Wear test conditions>
Dimensions of cylindrical specimen: outer diameter 30 mm, inner diameter 16 mm, axial dimension 10 mm
Surface roughness (Ra) of cylindrical specimen: 0.005 to 0.010 μm
Rotational speed of driving specimen: 10 min ^-1
Rotational speed of driven specimen: 7 min ^-1
Slip rate: 30%
Sliding distance: 3000m
Lubricating oil: Spindle oil # 10
Surface pressure: 1.2 GPa

[Burn-in test]
In addition, in the same manner as each ball 3 of sample Nos. 1 to 16, four spheres (diameter 12.7 mm) for a four-ball tester compliant with “ASTM D 2596” are produced and burned under the following conditions. A test was conducted.
In this four-ball tester, first, three spheres are arranged and fixed so that all the spheres are in contact with each other and the spheres are the vertices of an equilateral triangle, and on the depression formed by these fixed spheres. The same sphere (rotating sphere) as the fixed sphere was placed with the traction oil “VG22” applied.

Next, this rotating sphere was rotated under the conditions of surface pressure: 2.0 GPa and rotation speed: 3000 min ⁻¹ , and the time until the torque became 5 times the initial value was measured as “burn-in life”. Then, by dividing the measured value of each sample by the measured value of sample No. 9, a “burn-in life ratio” in which the burn-in life of sample No. 9 was set to “1” was obtained. The results are also shown in Table 2 below.

[Fretting resistance test]
In addition, the ball (diameter 7 mm) for “35TAC ball bearing” is manufactured in the same manner as each ball 3 of sample Nos. 1 to 16, and the inner ring and outer ring are made of SUJ2 and subjected to normal heat treatment including soaking. It was produced by. A thrust angular ball bearing for ball screw support shown in FIG. 2 was assembled using the obtained balls 3, the inner ring 1, the outer ring 2, and the cage 4.
First, each obtained bearing was attached to an anderometer, and an initial vibration value (Anderon value) was measured in each frequency range of “LB”, “MB”, and “H.B.”. . Next, each bearing is attached to a swing test device, and lubricating oil: spindle oil # 10, preload: 14.7 N, swing angle: 8 °, swing frequency: 30 Hz (30 swings per second) It was swung 100,000 times under the conditions of

Next, each bearing after the swing test is attached to an anderometer, and the vibration value (Anderon value) after the test is set to each frequency of “LB”, “MB”, and “H.B.”. Measured in range. Next, the ratio of the vibration value after the test to the initial vibration value was calculated. The results are also shown in Table 2 below. The smaller the vibration value by the andrometer, the higher the fretting resistance.
No. 8 could not be tested because cracks occurred when the balls 3, cylindrical test pieces, and spheres were ground after heat treatment.

In Table 2, numerical values deviating from the configuration of the present invention are underlined. A case where all items of the configuration of the ball are not underlined corresponds to an example of the present invention, and a case where any component is underlined corresponds to a comparative example. In Table 2, “(Si, Mn) N” indicates “abundance ratio of Si / Mn nitride having a particle diameter of 1 μm or less on the rolling surface”, and “γ _R ” indicates “the surface layer portion of the rolling surface. The amount of retained austenite is shown.

  As can be seen from Table 2, on the rolling surface of the ball 3, Si · Mn nitride having a particle size of 1 μm or less is present in an area ratio of 1% or more and 10% or less. The ball bearings of Sample Nos. 1-4, 6, and 7 in which the retained austenite is 1% by volume or more and 10% by volume or less are compared with the ball bearings of Samples No. 5 and 8-16 that do not satisfy any of these. High wear resistance, seizure resistance, fretting resistance, and durability.

Thereby, the ball 3 of the bearing shown in FIGS. 1 and 2 is configured as Sample Nos. 1-4, 6, and 7 corresponding to the embodiment of the present invention, so that it is a rolling bearing or belt type that supports the ball screw. Fretting resistance and seizure resistance sufficient as a rolling bearing for a continuously variable transmission can be obtained.
As can be seen from Tables 1 and 2, the silicon (Si) content of the steel used is 0.4 mass% or more, the manganese (Mn) content is 0.4 mass% or more, silicon (Si) and manganese When the total content of (Mn) is 1.0% by mass or more, Si / Mn nitride having a particle size of 1 μm or less can be present on the rolling surface of the balls 3 in an area ratio of 1% or more.

It is sectional drawing which shows the ball bearing corresponded to one Embodiment of this invention. It is sectional drawing which shows the ball bearing corresponded to one Embodiment of this invention. It is the figure which showed typically the belt type continuously variable transmission of the vehicle.

Explanation of symbols

1 Inner ring 2 Outer ring 3 Ball (rolling element)
4 Cage 11a Rolling bearing 11b Rolling bearing 12a Rolling bearing 12b Rolling bearing 7 Input shaft pulley 8 Output shaft pulley 9 Belt

Claims (2)

The rolling elements are
The carbon (C) content is 0.3% by mass to 1.2% by mass, the chromium (Cr) content is 0.5% by mass to 2.0% by mass, and the silicon (Si) content is 0.4 mass% or more and 1.2 mass% or less, manganese (Mn) content is 0.4 mass% or more and 1.2 mass% or less, and the total content of silicon (Si) and manganese (Mn) is 1. 0 mass% or more and 2.0 mass% or less, the remaining iron and the steel material which is an unavoidable impurity are processed into a predetermined shape, and then subjected to heat treatment including nitriding treatment or carbonitriding treatment and quenching and tempering. Obtained,
Si / Mn nitrides composed of silicon (Si) nitride and manganese (Mn) nitride and having a particle size of 1 μm or less exist on the rolling surface in an area ratio of 1% to 10%. A rolling bearing characterized in that the retained austenite in the surface layer portion is 10% by volume or less.   The bearing ring has a carbon (C) content of 0.2 mass% to 1.2 mass%, a chromium (Cr) content of 0.5 mass% to 2.0 mass%, silicon (Si) Steel content that is 0.1 mass% to 0.5 mass%, manganese (Mn) content is 0.1 mass% to 0.5 mass%, the remaining iron and inevitable impurities The rolling bearing according to claim 1, wherein the rolling bearing is obtained by heat-treating after processing into a predetermined shape.

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